Production of alkali-soluble cellulosic textile materials by the nitric acid treatment of partially etherified cottons



United States Patent 3,087,775 PRODUCTION OF ALKALI-SOLUBLE CELLULOSICTEXTILE MATERIALS BY THE NITRIC ACID gllzgTMENT 0F PARTIALLY ETHERIFIEDCOT- Robert M. Reinhardt and Terrence W. Feuner, New Orleans, La.,assignors to the United States of America as represented by theSecretary of Agriculture N0 Drawing. Filed June 1, 1960, Ser. No. 33,3508 Claims. (Cl. 8-116) (Granted under Title 35, U.S. Code (1952), sec.266) A non-exclusive, irrevocable royalty-free license in the inventionherein described, throughout the world for all purposes of the UnitedStates Government, with the ,7 power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States ofAmer- This invention relates to alkali-soluble cellulosic textilematerials and methods of their production.

It is known that certain chemical modifications of cotton can beemployed to prepare cellulosic derivatives which are alkali-soluble.However, many of those chemical modifications involve the use of theuneconomical reagents and/ or uneconomical conditions of reaction.Further, many of these chemical modifications results in nonfibrousproducts or products which are so weakened and degraded that their valueas textile materials is lost.

To be a useful article of commerce for textile usage, an alkali-solublecellulosic textile material must possess enough strength to withstandthe rigorous stresses and strains of processing on normal textilemachinery. Along with these substantial strength requirements, becauseof the transient uses for which these textile materials are employed,their solubility must be suflicient to allow essentially completeremoval of these textile members without undue complications to normalplant practices.

It is an object of this invention to provide a process for theproduction of alkali-soluble cellulosic textile materials which possessthe strength and solubility characterics necessary for industrialutilization. This objective is accomplished by a two step treatment:first, cotton textile materials are partially etherified to a low degreeof substitution (D.S., the average number of substituent ether groupsper anhydroglucose unit), in the range of from about 0.01 to about 0.6,and secondly, treatment of the partially etherified cotton with aqueoussolutions of nitric acid. The process may be carried out on fabric,thread, yarn, or fiber.

It is a further objective of this invention to provide a process whichis more economical than convention-a1 processes in that only inexpensivereagents are used and in that more economical reaction conditions,notably shorter reaction times, lower reaction temperatures, and moredilute concentrations of reagent may be employed in the nitricacidtreatment step than would be operative without the unique complementaryefiect of the combined steps of the two step process.

As is known to those skilled in the art, nitric acid treatments ofcellulose have been used to prepare alkalisoluble materials. In theprior art, however, the products have been either highly nitratedmaterials (nitrocellulose) prepared under rigorous, usually anhydrous,reaction conditions with nitric acid and strong dehydrating agents, ormaterials nitrated to a lower degree but under conditions requiringmixed reagent techniques such as the use of nitric acid-phosphoric acidor nitric acid-sulfuric acid solutions, or materials which are nottextile fibers but are produced in solution or are cast as films.

In the present invention the nitric acid treatment is carried out onpartially etherified cottons. It is not necessary to use anhydrousconditions, dehydrating compounds 3,087,775 Patented Apr. 30, 1963 ormixed acid techniques. A fibrous product is produced which has goodstrength and is soluble in alkaline solutions. Further, by usingpartially etherified cottons instead of native or mercerized cotton as astarting material, less drastic conditions may be employed in nitricacid treatment step. With partially etherified cottons, products withhigher solubility are obtained with more dilute concentrations of nitricacid, shorter treatment times, and lower temperatures than if the nitricacidtreatment was carried out on native or mercerized cotton.

The two step treatment accomplishes the objectives through multipleefiects. In the first or partial etherification step, a small amount ofether groups are introduced. These ether groups are alkali-solubilizingand would result in a alkali-soluble material if the etherification wascarried out to greater extent. Further, these other groups exert aswelling effect which makes the partially etherified cotton highlyaccessible for reaction in the nitric acid treatment step.

The preferred partially etherified cottons which may be employed in theprocess of this invention include partially aminoethylated,carbamoylethylated, carboxyethylated, carboxymethylated, cyanoethylated,hydroxyethylrated, and phosphonomethylated cotton.

In the second or nitric acid treatment step, three chemical reactionsmay take place: nitration of cellulosic bydroxyls, oxidation along thecellulosic chain, and hydrolysis of glucosidic linkages of thecellulosic chain. All three reactions are efficacious in producingalkalisolubility. v

In the nitric acide treatment step, nitration of the cellulosichydroxyls proceeds only to a low degree as evidenced by a modifiedKjeldahl nitrogen analysis of the products. The nitrogen introduced isusually 1.2% or less. The low extent of oxidation during this step maybe estimated by carboxyl and carbonyl analysis. Although some hydrolyticcleavage of glucosidic linkages takes place, this cleavage is notextensive as evidenced by the considerable strength retained by theproduct. Drastic loss of strength is a consequence of a relatively smallamount of cleavage of glucosidic linkages. The extent of this cleavagemay be more accurately estimated by DR (degree of polymerization)determinations.

No claim is made singly for the partial etherification or for the nitricacid treatment step. The process of this invention utilizes the uniquecomplementary or synergistic effect of the combination of the twotreatments.

The partial etherification step may be carried out by any of the knownmethods which will be apparent to those skilled in the art.

Partial aminoethylation of cotton may be carried out, for example, asdescribed by Guthrie in Textile Research Journal 17, 625-9 (1957). Theaminoethyl ether of cellulose may be represented by the formula in whichR represents the anhydroglucose unit.

Partial carbamoylethylation of cotton may be carried out, for example,as described by Frick, Reeves, and Guthrie in Textile Research Journal27, 2949 (1957). The carbamoylethyl ether of cellulose may berepresented by the formula ROCH CH C(O)NH in which R represents theanhydroglucose unit.

Partial car-boxyethylation of cotton may be carried out, for example, asdescribed by Daul, Reinhardt, and Reid in Textile Research Journal 25,246-53 (1955). The carboxyethyl ether of cellulose may be represented bythe fiormula ROCH CH COOH in which R represents the anhydroglucose unit.

Partial carboxymethylation of cotton may be carried out, for example, asdescribed by Daul, Reinhardt, and Reid in Textile Research Journal 22,787-92 (1952). The

3 carboxymethyl ether of cellulose may be represented by the formulaROCH COOH in which R represents the anhydroglucose unit.

Partial cyanoethylation of cotton may be carried out, for example, asdescribed by Daul, Reinhardt, and Reid in Textile Research Journal 25,24653 (1955) The cyanoethyl etherof cellulose may be represented by theformula ROCH CH CN in which R represents the anhydroglucose unit.

Partial hydroxyethylation of cotton-may be carried out, for example, asdescribed by Lawrie, Reynolds, and Ward in Journal of the Society ofDyers and Colourists 56, 6-17 (1940) The hydroxyethyl ether of cellulosemay be represented by the formula ROCH CH OI-I in which R represents theanhydroglucose unit.

Partial phosphonomethylation of cotton may be carried out, for example,as described by Drake, Reeves, and Guthrie in Textile Research Journal29, 270- 1959). The phosphonomethyl ether of cellulose may berepresented' by the formula ROCH P(O) (OH) in which R represents theanhydroglucose unit.

Partially etherified cottons with a degree of substitution of from about0.04 to about 0.55 are preferred for the process of this invention. Thedegree of substitution and the severity of conditions required in thenitric acid treatment for good alkali-solubility are inversely related.

In the present invention, the nitric acid treatment step may be carriedout within widely varying limits. The treatment may be effected attemperatures ranging from about room temperature to boiling and atnitric acid concentrations varying from about 10% to about 70%. Withhigher temperatures, the treatment time is reduced'and may be as littleas a few seconds. The treatment temperature is correspondingly adjustedin inverse relation to treatment time. With the lower concentrations ofnitric acid the time of treatment required is extended and may range toperiods of 24 hours or longer. For the lower con centrations of nitricacid, the time of treatment necessary may thus be reduced by anadjustment towards higher temperatures.

The preferred range of conditions for the nitric acid treatment'stepthus encompasses treatment times of from about 0.5 minute to about 75'minutes, at temperatures of from about room temperature to the boilingtemperature of the nitric acid solution, using concentrations'of nitricacid of about 10% to about 70%, the time and temperature of the nitricacid treatment being inversely related to thenitric acid concentration.

Uses for alkali-soluble textile material are well known in the art.Among such uses are the preparation of open work fabrics byweavingsoluble yarns and ordinary yarns in such a manner that upondissolution of the soluble yarns the open-work pattern eifect isproduced in the fabric. Other uses may include utilization ofalkali-soluble threads for basting or for connecting threads in thestring-sock knitting process. The soluble members are readily removed bya subsequent alkali treatment. Alkalisoluble fabric is used as a backingcloth in a process for the manufacture of lace,

Having thus described in a general way the operation of the process ofthis invention, details of the process are listed below in specificexamples which illustrate the application of' the process to cottontextile materials.

The following laboratory techniques were used for determination ofstrength and alkali-solubility of the products.

Determination of strength-The strength of the cellulosic textilematerialswas determined on one-inch strips by the standard test methodof the American Society for Testing Materials as specified by A.S.T.M.Committee D-13 in Standard General Methods of Testing Woven TextileFabrics, Philadelphia, Pennsylvania, 1951, test method D39-49. Theresults are-expressed as the percentage of the original strength of thefabric which is retained after the treatment.

Determination of alkali-solubility.-Approximately one gram ofair-equilibrated cellulose textile material was accurately weighed on ananalytical balance. The sample was transferred to a flask containing aboiling 10% aqueous solution of sodium hydroxide in an amount sufficientto give a :1 liquor to sample ratio, by weight. The solution containingthe sample was maintained at boiling for 10 minutes. At the end of thisperiod, the solution and residue were quantitatively transferred to apreviously weighed centrifuge tube. The tube was then centrifuged for 8minutes at 1700 r.p.m. to affect separation of the residue and clearsupernatant solution. The solution was decanted and the residue washedtwice with distilled water, twice with dilute acetic acid solution, andthen four times with distilled water. The residue was then dried,equilibrated, and weighed in the analytical balance. From the weight ofthe residue, the alkali-solubility of the sample was calculated:

Percent alkali-solubility=l00[W EXAMPLE 1 Samples of cotton cloth were:(a) mercerized by treatment with 20% sodium hydroxide; (b)aminoethylated to a D.S. of 0.08 by treatment with Z-aminoethyl sulfuricacid and 40% sodium hydroxide; (c) carbamoylethylated to a D.S. of 0.25by impregnation with an aqueous solution containing 50% acrylamide and4% sodium hydroxide followed by heating at C. for five minutes; (d)carboxyethylated to a D.S. of 0.12 by hydrolysis of partiallycyanoethylated cotton with 20% sodium hydroxide solution for 16 hours at25 C.; (e) carboxymethylated to a D.S. of 0.10 by treatment with 17%aqueous chloro- -acetic acid and 50% sodium. hydroxide solution; (f)cyanoethylated to a D.S. of 0.55 by impregnation with 2% sodiumhydroxide solution followed by treatment with acrylonitrile at 55 Q; (g)hydroxyethylated to a D.S. of 0.25 byimpregnation with 7% sodiumhydroxide solution-followed. by treatment with 10% ethylene oxide inperchloroethylene at 25 C.; (h) phosphonomethylated to a D.S. of 0.04 bytreatment with 6.8% disodium salt of chloromethylphosphonic acid in thepresence of 25% sodium hydroxide. The fabrics were washed and dried.They were then treated with an aqueous solution containing 70% nitricacid, by weight, for 30 minutes at 26 C. (room temperature), andthoroughly washed with distilled water and dried. Thealkali-solubilities of the treated samples are shown in the followingtable.

Table I Alkali-solubility,

Fabric treated with nitric acid: Percent Mercerized cotton 65.6Aminoethylated cotton 97.1 Carbamoylethyla-ted cotton 80.5

Carboxyethylated cotton 100.0

Carboxymethyla-ted cotton 98.3 cyanoethylated cotton 96.3Hydroxyethylated cotton 82.7 Phosphonomethylated cotton 82.8

EXAMPLE 2 A sample of cotton was hydroxyethyl-ated to a D.S. of 0.5'0-bytreatment similar to that of sample (g) of Example 1. It was treatedwith nitric acid as in Example 1. The alkali-solubility was 89.5%.

EXAMPLE 3 Samples of partially carboxymcthylated cotton, D.S. 0.10, weretreated with aqueous solutions containing 70% nitric acid, by weight, at26 C. for various periods of time of from minutes to 75 minutes. Forcomparison, a sample of mercerized cotton was treated for 75 minutes.The properties of the treated samples are shown in the EXAMPLE 5 Samplesof partially carboxymethylated cotton (D.S. 0.08) and of mercerizedcotton cloth were treated with an aqueous solution containing 70% nitricacid, by weight, at 40 C. for 5 minutes. The nitric acidtreatedcarboxymethylated tabric was 88.4% alkali soluble and retained73.5% of its original strength. The nitric acid treated mercerizedfabric was only 53.0% alkali-soluble and retained 89.4% of its originalstrength.

EXAMPLE 6 Samples of partially carboxymethylated cotton (D.S. 0.08) andot mercerized cotton were treated with an aqueous solution containing35% nitric acid, by weight, at the boil for 0.5 minute.Alkali-solubilities were 96.3% and 27.9%, respectively.

EXAMPLE 7 Samples of partially carboxymethylated cotton (D.S. 0.08) andof mercerized cotton were treated with an aqueous solution containing10% nitric acid, by weight, at the boil for 4 minutes.Alkalisolubilitics were 96.7% and 53.2%, respectively.

We claim:

1. A process for producing an aqueous alkali soluble cotton cellulosictextile material which comprises etherit'ying the cotton cellulosictextile material to a degree of substitution of from about 0.01 to about0.6 and oxidizing the cellulose chain of the partially etherifiedtextile material by treating the partially etherified cotton cellulosictextile material with an aqueous solution of nitric acid in aconcentration of from about 10% to about by weight, at a temperature offrom about room temperature to that of the boiling point of the aqueousnitric acid solution, tor a period of time of trout about 0.5 minute toabout minutes, the time and temperature of the nitric acid treatmentbeing inversely related to the nitric acid concentration.

2. The process of claim 1 in which the partial etherification employedis aminoethylation.

3. The process of claim 1 in which the partial etherification employedis carbamoylethylat-ion.

4. The process of claim 1 in which the partial etherification employedis icarboxyet-hylation.

5. The process of claim 1 in which the partial etherification employedis carboxymethyl-ation.

6. The process of claim 1 in which the partial etherification employedis cyanoethyl-ation.

7. The process of claim 1 in which the partial etherification employedis hydroxyethylation.

8. The process of claim 1 in which the partial etherification employedis phosphonomethylation.

References Cited in the file of this patent UNITED STATES PATENTS DatlowFeb. 15, 1949 OTHER REFERENCES Lawrie et al.: J. of the Soc. of 'Dyersand Colourists, 56 pp. 6-17, 1940.

Guthrie: Textile Research J ournal 17, pp. 625-629, 1947.

Erick et al.: Textile Research J. 27, pp. 294-299, 1957.

-D-aul et al.: Textile Research J. 25, pp. 246-253, 1955.

Daul et al. Textile Research J. 22, pp. 787-792, 1952.

Daul et a1; Textile Research J. 25, pp. 246-253, 1955.

Drake et al.: Textile Research J. 29, pp. 270-275, 1959'.

Reinhardt et a1.: Industrial and Engineering Chemistry, vol. 50, No. 1,January 1958, pp. 83-86.

Reinhardt et al.: Textile Research Journal, vol. XXIX, No. 10, October1959, pp. 802-810, particularly p. 810. l

1. A PROCESS FOR PRODUCING AN AQUEOUS ALKALI SOLUBLE COTTON CELLULOSIC TEXTILE MATERIAL WHICH COMPRISES PARTIALLY ETHERIFYING THE COTTON CELLULOSE TEXTILE MATERIL TO A DEGREE OF SUBSTITUTION OF FROM ABOUT 0.01 TO ABOUT 0.6 AND OXIDIZING THE CELLULOSE CHAIN OF THE PARTIALLY ETHERIFIED TEXTILE MATERIAL BY TREATING THE PARTIALLY ETHERIFIED COTTON CELLULOSIC TEXTILE MATERIAL WITH AN AQUEOUS SOLUTION OF NITRIC ACID IN A CONCENTRATION OF FROM ABOUT 10% TO ABOUT 70% BY WEIGHT, AT A TEMPERATURE OF FROM ABOUT ROOM TEMPERATURE TO THAT THE BOILING POINT OF THE AQUEOUS NITRIC ACID SOLUTION, FOR A PERIOD OF TIME OF FROM ABOUT 0.5 MINUTE TO ABOUT 75 MINUTES, THE TIME AND TEMPERATURE OF THE NITRIC ACID TREATMENT BEING INVERSELY RELATED TO THE NITRIC ACID CONCENTRATION 